Capacitive micromachined ultrasonic transducer, method for preparing the same, panel, and device

Abstract

The present disclosure provides a capacitive micro-machined ultrasonic transducer, a method for preparing the same, a panel, and a device, and belongs to the technical field of ultrasonic imaging. A capacitive micro-machined ultrasonic transducer includes a first electrode, a vibrating diaphragm layer and a second electrode that are arranged in order from bottom to top, a cavity existing between the first electrode and the vibrating diaphragm layer, in which the capacitive micro-machined ultrasonic transducer further includes a third electrode located on a surface of the vibrating diaphragm layer proximate to the cavity, an orthogonal projection of the third electrode on the first electrode covers a part of an orthogonal projection of the cavity on the first electrode. The technical solution of the present disclosure can realize the conversion of the frequency of the ultrasonic waves emitted by the capacitive micro-machined ultrasonic transducer.

What is claimed is: 
     
       1. A capacitive micro-machined ultrasonic transducer, comprising a first electrode, a vibrating diaphragm layer and a second electrode that are arranged in order from bottom to top,
 wherein a cavity exists between the first electrode and the vibrating diaphragm layer, 
 wherein the capacitive micro-machined ultrasonic transducer further comprises a third electrode located on a surface of the vibrating diaphragm layer proximate to the cavity, and an orthogonal projection of the third electrode on the first electrode covers a part of an orthogonal projection of the cavity on the first electrode, and 
 wherein the first electrode and the third electrode are configured such that, after electrical signals of different polarities are applied, the third electrode moves to the first electrode under the action of an electric field so that a thickness of a portion of the cavity corresponding to the third electrode in a direction perpendicular to the first electrode is 0. 
 
     
     
       2. The capacitive micro-machined ultrasound transducer of  claim 1 , wherein the orthogonal projection of the cavity on the first electrode covers the orthogonal projection of the third electrode on the first electrode, and the third electrode comprises at least one hollowed-out area. 
     
     
       3. The capacitive micro-machined ultrasonic transducer of  claim 2 , wherein the orthogonal projection of the cavity on the first electrode is a first circle, an orthogonal projection of the hollowed-out area on the first electrode is a second circle, and a diameter of the second circle is smaller than a diameter of the first circle. 
     
     
       4. The capacitive micro-machined ultrasound transducer of  claim 2 , wherein the third electrode comprises two, three or four hollowed-out areas. 
     
     
       5. The capacitive micro-machined ultrasound transducer of  claim 1 , further comprising a signal line connected to the third electrode. 
     
     
       6. The capacitive micro-machined ultrasound transducer of  claim 1 , wherein a lower surface of the third electrode proximate to the first electrode is substantially flush with a lower surface of the vibrating diaphragm layer proximate to the first electrode. 
     
     
       7. The capacitive micro-machined ultrasonic transducer of  claim 1 , wherein the vibrating diaphragm layer is provided with a via hole communicating with the cavity, the capacitive micro-machined ultrasonic transducer further comprises a filling structure, a part of the filling structure fills the via hole, and the other part of the filling structure is located in the cavity. 
     
     
       8. The capacitive micro-machined ultrasonic transducer of  claim 7 , wherein a diameter of the via hole is in a range from 1 μm to 10 μm. 
     
     
       9. The capacitive micro-machined ultrasound transducer of  claim 1 , wherein the vibrating diaphragm layer comprises a first portion corresponding to the cavity and a support portion other than the first portion, and an orthogonal projection of the first portion on the first electrode coincides with the orthogonal projection of the cavity on the first electrode. 
     
     
       10. The capacitive micro-machined ultrasound transducer of  claim 1 , wherein a thickness of the cavity in a direction perpendicular to the first electrode is in a range from  1  nm to 10 μm. 
     
     
       11. The capacitive micro-machined ultrasound transducer of  claim 1 , further comprises an insulating layer on a surface of the second electrode away from the first electrode. 
     
     
       12. The capacitive micro-machined ultrasound transducer of  claim 1 , wherein a material of the third electrode is same as a material of the second electrode; and/or a material of the third electrode is same as a material of the first electrode. 
     
     
       13. A capacitive micro-machined ultrasonic transducing panel, comprising a plurality of capacitive micro-machined ultrasonic transducers of  claim 1  that are arranged in an array. 
     
     
       14. A capacitive micro-machined ultrasonic transducing device, comprising the capacitive micro-machined ultrasonic transducing panel of  claim 13  and a driving circuit, wherein the driving circuit is connected to the first electrode and the third electrode of the capacitive micro-machined ultrasonic transducer, and configured to apply electrical signals of different polarities to the first electrode and the third electrode. 
     
     
       15. A method for preparing a capacitive micro-machined ultrasonic transducer, comprising forming a first electrode, a vibrating diaphragm layer, and a second electrode that are arranged in order from bottom to top, wherein a cavity exists between the first electrode and the vibrating diaphragm layer;
 the method further comprises forming a third electrode located on a surface of the vibrating diaphragm layer proximate to the cavity, wherein an orthogonal projection of the third electrode on the first electrode covers a part of an orthogonal projection of the cavity on the first electrode, and the first electrode and the third electrode are configured such that, after electrical signals of different polarities are applied, the third electrode moves to the first electrode under the action of an electric field so that a thickness of a portion of the cavity corresponding to the third electrode in a direction perpendicular to the first electrode is 0. 
 
     
     
       16. The method for preparing a capacitive micro-machined ultrasonic transducer of  claim 15 , further comprises forming a signal line connected to the third electrode. 
     
     
       17. The method for preparing a capacitive micro-machined ultrasonic transducer of  claim 16 , wherein the signal line and the third electrode are formed by a signal patterning process. 
     
     
       18. The method for preparing a capacitive micro-machined ultrasonic transducer of  claim 15 , wherein the vibrating diaphragm layer is provided with a via hole communicating with the cavity,
 the method further comprises forming a filling structure, wherein a part of the filling structure fills the via hole, and the other part of the filling structure is located in the cavity. 
 
     
     
       19. The method for preparing a capacitive micro-machined ultrasonic transducer of  claim 15 , wherein the forming the cavity comprises:
 forming a sacrificial layer on the first electrode; 
 forming a third electrode on the sacrificial layer; 
 forming a vibrating diaphragm layer covering the third electrode and the sacrificial layer, wherein the vibrating diaphragm layer has a via hole exposing the sacrificial layer; and 
 removing the sacrificial layer through the via hole, to form the cavity between the vibrating diaphragm layer and the first electrode.